1. Field of the Invention
The present invention relates to drafting instruments and more particularly to a parallel bar having a slider indicating increments of movement of the bar with respect to the drawing board.
2. Description of the Prior Art
Drafting instruments commonly known as parallel bars, such as is disclosed by U.S. Pat. Nos. 1,075,067 and 1,310,596, as well as other types presently in use, are well known. U.S. Pat. No. 1,310,596 discloses a parallel bar movement indicator secured to the guide cable but neither of these patents nor other types of parallel bars presently in use, so far as I know, disclose a hairline slider which may be selectively positioned along the bar for indicating increments of movement of the parallel bar with respect to a base line or reference point when the bar is moved along the Y-axis of a rectangular coordinate.
This invention provides a measuring member scale supported by the base of a parallel bar and further includes a slider containing a hairline with the slider secured to one of the parallel bar guide cables so that the slider is moved toward one end or the other of the parallel bar as it is moved in respective directions along the Y-axis. The distance of movement is indicated by the position of the hairline with respect to the underlying parallel bar supported scale.